feat(asg): Add fine-grained options for schedule_config scale_in and scale_out

Author: baolsen

README.md

@@ -148,7 +148,34 @@ Once you have created the parameter, you must remove the variable `runners_token
 
 Finally, the runner still supports the manual runner creation. No changes are required. Please keep in mind that this setup will be removed in future releases.
 
-### Auto Scaling Group Instance Termination
+### Auto Scaling Group
+
+#### Scheduled scaling
+
+When `enable_schedule=true`, the `schedule_config` variable can be used to scale the Auto Scaling group. 
+
+Scaling may be defined with one `scale_out` scheduled action and/or one `scale_in` scheduled action.
+
+For example:
+```hcl
+  module "runner" {
+    ...
+    enable_schedule = true
+    schedule_config = {
+      # Configure optional scale_out scheduled action
+      scale_out_recurrence = "0 8 * * 1-5"
+      scale_out_count      = 1 # Default for min_size, desired_capacity and max_size
+      # Override using: scale_out_min_size, scale_out_desired_capacity, scale_out_max_size
+
+      # Configure optional scale_in scheduled action
+      scale_in_recurrence  = "0 18 * * 1-5"
+      scale_in_count       = 0 # Default for min_size, desired_capacity and max_size
+      # Override using: scale_out_min_size, scale_out_desired_capacity, scale_out_max_size
+    }
+  }
+```
+
+#### Instance Termination
 
 The Auto Scaling Group may be configured with a
 [lifecycle hook](https://docs.aws.amazon.com/autoscaling/ec2/userguide/lifecycle-hooks.html)

main.tf

@@ -192,19 +192,19 @@ resource "aws_autoscaling_schedule" "scale_in" {
   autoscaling_group_name = aws_autoscaling_group.gitlab_runner_instance.name
   scheduled_action_name  = "scale_in-${aws_autoscaling_group.gitlab_runner_instance.name}"
   recurrence             = var.schedule_config["scale_in_recurrence"]
-  min_size               = var.schedule_config["scale_in_count"]
-  desired_capacity       = var.schedule_config["scale_in_count"]
-  max_size               = var.schedule_config["scale_in_count"]
+  min_size               = try(var.schedule_config["scale_in_min_size"], var.schedule_config["scale_in_count"])
+  desired_capacity       = try(var.schedule_config["scale_in_desired_capacity"], var.schedule_config["scale_in_count"])
+  max_size               = try(var.schedule_config["scale_in_max_size"], var.schedule_config["scale_in_count"])
 }
 
 resource "aws_autoscaling_schedule" "scale_out" {
   count                  = var.enable_schedule ? 1 : 0
   autoscaling_group_name = aws_autoscaling_group.gitlab_runner_instance.name
   scheduled_action_name  = "scale_out-${aws_autoscaling_group.gitlab_runner_instance.name}"
   recurrence             = var.schedule_config["scale_out_recurrence"]
-  min_size               = var.schedule_config["scale_out_count"]
-  desired_capacity       = var.schedule_config["scale_out_count"]
-  max_size               = var.schedule_config["scale_out_count"]
+  min_size               = try(var.schedule_config["scale_out_min_size"], var.schedule_config["scale_out_count"])
+  desired_capacity       = try(var.schedule_config["scale_out_desired_capacity"], var.schedule_config["scale_out_count"])
+  max_size               = try(var.schedule_config["scale_out_max_size"], var.schedule_config["scale_out_count"])
 }
 
 data "aws_ami" "runner" {

variables.tf

@@ -636,10 +636,15 @@ variable "schedule_config" {
   description = "Map containing the configuration of the ASG scale-in and scale-up for the runner instance. Will only be used if enable_schedule is set to true. "
   type        = map(any)
   default = {
-    scale_in_recurrence  = "0 18 * * 1-5"
-    scale_in_count       = 0
+    # Configure optional scale_out scheduled action
     scale_out_recurrence = "0 8 * * 1-5"
-    scale_out_count      = 1
+    scale_out_count      = 1 # Default for min_size, desired_capacity and max_size
+    # Override using: scale_out_min_size, scale_out_desired_capacity, scale_out_max_size
+
+    # Configure optional scale_in scheduled action
+    scale_in_recurrence = "0 18 * * 1-5"
+    scale_in_count      = 0 # Default for min_size, desired_capacity and max_size
+    # Override using: scale_out_min_size, scale_out_desired_capacity, scale_out_max_size
   }
 }